Reported were four experiments which investigated the developmental and mental retardation aspects of an initial stage of visual information processing termed iconic memory. The stage was explained to involve processing visual stimuli prior to sensation and through to recognition. In three of the four experiments, the paradigm of visual masking was used to determine the speed or efficiency of information processing; the Crawford-pattern mask technique was used throughout. The four experiments were titled age effects on backward visual masking, adult age effects on backward visual masking, forward and backward masking with normal and retarded subjects, and iconic storage and information availability by normal and retarded subjects, respectively. Subjects in the four experiments ranged in age from 5 to 55 years of age. Major findings of the experiments were reported to be development and documentation of a methodology surmounting previous problems in studying development and mental retardation aspects of iconic memory, establishment of relationship between age variable and efficiency with which visual information is processed, and poorer performance by retarded subjects on iconic memory tasks than by normal subjects matched in terms of mental age. (CB)